Device for taking up wear for a disc brake and a brake including said device

ABSTRACT

This device for automatically taking up wear for a brake having a disc and a brake pad caliper controlled hydraulically and/or mechanically is of the type having a screw, a nut and a piston exerting a pressure on the screw. A ring having oblique teeth and slidably keyed on the screw meshes with a radial finger member. When braking the ring advances with the screw. When the braking ceases, the screw moves back immediately but as the ring is axially movable, it only moves back under the effect of springloaded finger members when the screw and nut system is no longer under load and then rotates, if necessary, the screw with respect to the nut. Any risk of jamming of the device taking up wear is avoided and the wear is taken up irrespective of the control means employed, namely hydraulic or mechanical.

[ DEVICE FOR TAKING UP WEAR FOR A DISC BRAKE AND A BRAKE INCLUDING SAIDDEVICE [75] Inventor: Jean-Marc Laurent Hauth,

Pont-A-Mousson, France [73] Assignee: Pont-A-Mousson S.A.,

Pont-A-Mousson, France [22] Filed: June 9, 1972 [21] Appl. No.: 261,467

[30] Foreign Application Priority Data June 25, 1971 France 7123342 [52]U.S. Cl 188/196 BA, 188/719 [51] Int. Cl Fl6d 65/56 [58] Field of Search188/719, 79.5 GE, 188/106 F, 196 D, 196 BA [56] References Cited UNITEDSTATES PATENTS 2,669,327 2/1954 Chamberlain et al. 188/719 3,068,96412/1962 Williams et al. 188/196 D X 3,261,435 7/1966 Beatty 188/196 BAJuly 17, 1973 3,550,732 12/1970 Beller ..l88/7l.9

Primary ExaminerDuane A. Reger Attorney-Richard Sughrue, Robert J. Seas,Jr. et al.

[57] ABSTRACT This device for automatically taking up wear for a brakehaving a disc and a brake pad caliper controlled hydraulically and/ormechanically is of the type having a screw, a nut and a piston exertinga pressure on the screw. A ring having oblique teeth and slidably keyedon the screw meshes with a radial finger member. When braking the ringadvances with the screw. When the braking ceases, the screw moves backimmediately but as the ring is axially movable, it only moves back underthe effect of spring-loaded finger members when the screw and nut systemis no longer under load and then rotates, if necessary, the screw withrespect to the nut.

Any risk of jamming of the device taking 'up wear is avoided and thewear is taken up irrespective of the control means employed, namelyhydraulic or mechanical.

6 Claims, 5 Drawing Figures Patented July 17, 1973 3 Sheets-Sheet lPatented July- 17, 1973 3,746,133

3 Sheets-Sneet I5 DEVICE FOR TAKING UP WEAR FOR A DISC BRAKE AND A BRAKEINCLUDING SAID DEVICE The present invention relates to disc brakes forvehicles and more particularly to devices for automatically taking upwear of the brake pads.

It is well known in disc brakes automatically to compensate for the wearof the friction or brake pads by means of devices which take up wear andare of the screw and nut type in which one of the elements rotateswhereas the other is stationary. One of the elements is rotated, in thecourse of releasing the brake, through a ring which is connected torotate and move in translation with this element and is provided withteeth meshing with a finger member or lever which does not participatein the movements of the ring but is capable of moving away therefrom inopposition to elastically yieldable means. This type of device has adrawback. At the start of the release of the brake the pads are still incontact with the disc and the screw and nut system is still subjected toa large axial force on the part of the pads, so that, owing to frictionbetween the screw and the nut, no relative rotation can occur betweenthe screw and the nut and this has for consequence a jamming of thesystem which prevents the return of the pads or prevents the operationof the device for taking up wear.

An object of the present invention is to provide a device for taking upwear of the brake'pads for a disc brake which is improved in such manneras to overcome this drawback.

The invention provides a device of the aforementioned screw and nuttype, one of the elements being movable and moved by a toothed ringwhich is concentric with the movable element and co-operates with aradially movable finger member, wherein said ring, which has on itsouter face teeth which are parallel to each other and oblique relativeto the generatrices of the ring, is slidably keyed relative to themovable element and combined with resiliently yieldable thrust meanswhich bias the ring against said movable element.

Owing to the fact that the ring is slidably keyed relative to the movingelement of the screw and nut system, the rotation of the movable elementwith respect to the fixed element of the system is only brought about bythe rearward movement of the ring under the action of the thrust meanswhen the screw and nut system is no longer under load, whereby there isno longer any risk of the device taking up wear, jamming or failing toopcrate.

Another object of the invention is to provide a disc brake provided withthe improved automatic device for taking up wear.

Further features and advantages of the invention will be apparentlydescribed with reference to the accompanying drawings.

In the drawings:

FIG. 1 is a diagrammatic radial axial sectional view of a hydraulicallycontrolled disc brake provided with a device for automatically taking upwear according to the invention;

FIG. 2 is a diagrammatic sectional view taken on line 22 of FIG. 1;

FIG. 3 shows in the case of a limited amount of wear of the pads, adiagram in plan (A) and vertical sectional diagrams (B and C) relatingto the operation of the engagement of the toothed ring with the radialfinger member of the device according to the invention, the sections Band C being taken on line 3-3 of the diagram A;

FIG. 4 shows similar diagrams A, B, C in the case of a considerableamount of wear of the brake pads which requires to be taken upautomatically;

FIG. 5 is a diagrammatic sectional view of a modification of amechanically and hydraulically controlled disc brake improved inaccordance with the invention.

In the embodiment shown in FIGS. 1 and 2, the invention is applied to adisc brake having a disc 1 which is connected to rotate with a wheel tobe braked (not shown) and a caliper 2 which is slidable relative to thedisc 1 in a direction perpendicular to the latter.

The caliper carries, on one side of the disc 1, a friction or brake pad3 and, on the other side, a control cylinder device V combined with theimproved device D for automatically taking up wear.

The cylinder device V and the device D have a comnon cylindrical body 4which is in one piece with, or rigidly secured to, the caliper 2. Thebody 4 comprises on an axis X-X, parallel to the axis of the wheel to bebraked, a stepped cylinder or cavity 5, 6. A piston 7 of the cylinderdevice V is axially movable in the portion 5.

Placed on the end of the piston 7 is a support plate 8 which carries afriction or brake pad 9 adapted to bear against the opposite side of thedisc 1 to the pad 3. The support plate 8 is rendered integral with thepiston 7 by a pin 10.

The piston 7 is provided with a screwthreaded blind aperture 11 and thusconstitutes a nut in which is screwthreadedly engaged a screw 12 whosescrewthreaded portion is follwed by a smooth cylindrical bearing portion13 which is followed by a head 14 having a diameter exceeding thediameter of the bearing portion 13. The head is provided with axiallyextending studs 15 which are arranged along its peripheral marginalportion and are slidable in corresponding apertures 16 in a ring 17. Thelatter is slidable on the portion 13 of the screw 12 with respect towhich it is therefore slidably keyed. The ring has on its outer faceteeth 18 which are parallel to each other and oblique relative to thegeneratrices of the ring. These teeth 18 have a dissymetrical profile inthe form of saw teeth having a very inclined face 18 and a steep face18' (FIG. 2).

A finger member 19 is slidably keyed in a blind radial aperture 20formed in a member 21 secured to the body 4, for example by means of apin 22 which is fixed in the member 21 and extends into a slot 23 in thefinger member 19. The latter is resiliently biased by a spring 24 towardthe ring 17 against which it bears by its end portion which is providedwith teeth 25 (FIG. 3) corresponding to the teeth 18 of the ring withwhich they engage.

Finger members 26 parallel to the axis X-X are slidably mounted in blindapertures 27 in the body 4 and bear against the lateral face 28 of thering 17 under the action of springs 29.

Placed at the rear of the screw 12 is a flat piston 30 which is floatingand slidable in the second stepped portion 6 of the aperture of the body4 and screwed in the screwthreaded end portion of this stepped portion 6is a closing plug 31. An aperture 32 is an inlet for the fluid forcontrolling the brake which is supplied between the piston 30 and theplug 31 in the cylinder 6.

The device operates in the following manner When applying the brake, thecontrol fluid is supplied by way of the aperture 32 between the plug 31and the piston 30. Under the effect of this fluid, the piston 30 axiallyurges the screw 12 by acting on its head 14. The latter axially shiftsthe toothed ring 17. The screw 12 axially shifts the piston 7 which inturn causes the brake pad 9 to bear against the disc 1 through themedium of the support plate 8. In view of the fact that the caliper 2 isslidable, by reaction, the brake pad 3 bears against the disc 1 on theopposite side of the pad 9.

If the wear of the brake pads 3 and 9 is of small amount, when braking,the ring 17 moves to 17' (FIG. 3 and diagram A) through a distance Iwhich is less than the distance m corresponding to the axial advance ofthe ring necessary to ensure that a tooth of the ring, such as the tooth18 (diagrams A and B) engaged in a recess of the finger member 19,passes into the neighbouring recess of this finger member. Thefinger-member 19 thus moves away from the ring under the effect of theslight slope of the faces 18 of the teeth of the ring 17 and assumes theposition shown in diagram C but does not jump a tooth of this ring, sothat, when releasing the brake, the brake pads 3 and 9 are urgedrearwardly by the disc and carry along therewith the piston 7 and thescrew 12 with its head 14. The ring 17 is also urged rearwardly by thefinger members 26 under the action of the springs 29. Thus the fingermember 19 is caused to slide on the faces 18" having a slight slope ofthe teeth of the ring 17 without rotating the latter and the assembly isreturned to its initial condition (diagram B).

On the other hand, if the wear of the brake pads exceeds a certain valuein the course of braking, the ring 17 is moved a distance L exceedingthe distance m (see FIG. 4). The edges of the teeth 18 of the ring 17pass, in diagram A, from the position in full line to the position indotted line, that is the ring jumps one tooth under the finger member 19(compare in the diagrams B and C the positions assumed by the sectionsa, b, c,

d, of the four teeth). When ceasing the braking, the brake pads 3 and 9are urged rearwardly by the disc 1 and carry along therewith the piston7 and the screw 12 with its head 14. Owing to the fact that one toothhas been jumped and to the steep slope of the faces 18b of the teeth ofthe ring, the latter must, in order to be urged rearwardly by the fingermembers 26, rotate to the extent of one tooth, the tooth of section bfor example is substituted for the tooth of section a in diagram B androtate the screw 12 therewith. However, the screw 12 and the piston ornut 7 are still under load and cannot rotate with respect to each otherand there is therefore produced a rearward movement of the screw 12, itshead 14 and the studs 15 without a rearward movement of the ring 17.When the brake pads 3 and 9 are no longer in contact with the disc 1,the system comprising the screw 12 and the nut 7 is no longer under loadand one of the elements is able to rotate relative to the other so that,under the action of the springs 29 and finger members 26, the ring 17 isable to move rearwardly and cause the spring 12 to rotate in the nut 7,which is prevented from rotating by the pin 10, so as to lengthen thescrew and nut system and take up the wear of the pads and maintain at aminimum value the sum of the clearances j+g between the pads 3 and 9 andthe disc 1.

Owing to the fact that the ring 17 is not axially connected to the screw12 and to the sliding of the ring on the studs 15 of the screw whichrender the screw and the ring interconnected as concerns rotation, thewear of the brake pads 3 and 9 is taken up when this wear produces aclearance between the pads and the disc exceeding a certain value bylengthening the screw and nut system. This lengthening by rotation ofthe screw 12 in the nut 7 occurs under the effect of the rotation of thering 17 when the latter moves rearwardly. This rearward movement of thering 17 only occurs when the system comprising the screw 12 and the nut7 is no longer under load, that is, when the brake pads 3 and 9 are nolonger in contact with the disc 1. Thus, there is never any jamming ofthe system for taking up wear when releasing the brake.

According to the modification shown in FIG. 5, the invention is appliedto a brake having a combined hydraulic and mechanical control which thuspermits operating the brake either by the entry of fluid by way of theaperture 32 or by rotation of a control arm 33. The addition of amechanical control device modifies neither the device for taking up wearnor its operation. Indeed, instead of shifting the piston 30 by means ofa fluid when braking, the lever 33 is rotated so as to rotate a screw 34in a fixed nut 35. When the lever 33 is rotated, the screw 34 movestoward the disc and exerts pressure, while rotating, on a plate 36 whichexerts pressure through a rolling bearing 37 on a plate 38. The latterexerts a pressure on the piston 30 through an axial block 39 which isslidable in a piston 40 performing the function of a plug and appliedagainst the nut 35 when braking by means of the hydraulic control.

Owing to this arrangement, when the braking is performed by themechanical control or by the hydraulic control, the device for taking upwear operates since, irrespective of the control employed, it is thepiston 30 which operates the brake and its device for automaticallytaking up wear This is of particular advantage since the hydrauliccontrol or the mechanical control can be employed without increasing theclearance j f between the brake pads and the disc.

Having now described my invention what I claim as new and desire tosecure by Letters Patent is:

l. A device for taking up wear of brake pad means of a disc brake andadapted to be interposed between the brake pad means and thrust meansfor urging the brake pad means against the disc of the brake, saiddevice comprising means defining a body, a system having a longitudinalaxis and movable longitudinally relative to the body and comprising afirst element in the form of a screw and a second element in the form ofa nut coaxial with and screwthreadedly engaged with the screw, one ofsaid elements being rotatable about said axis relative to the body,means for preventing rotation of the other of said elements relative tothe body, a ring concentric with the rotatable element, means for keyingthe ring to the rotatable element so that the ring is slidable relativeto the rotatable element along said axis, first resiliently yieldablemeans for biasing the ring axially against the rotatable element, therotatable element having an outer peripheral portion having teeth whichare parallel to each other and oblique relative to radial axial planesof the ring, a finger member mounted in the body for movement radiallyof the ring and in engaging relation to the teeth, and secondresiliently yieldable means for biasing the finger member against theteeth.

2. A device as claimed in claim 1, wherein said mean keying the ring tothe rotatable element comprise axially extending studs integral with therotatable element and apertures in the ring into which apertures thestuds extend, the rotatable element having a shoulder against whichshoulder the ring is biased by the first resiently yieldable means.

3. A device as claimed in claim 1, wherein the first resilientlyyieldable means comprise axially extending finger members and springsbiasing the finger members against the ring.

4. A disc brake comprising a disc, a caliper, brake pad means, thrustmeans for urging the brake pad means against the disc, and a devicemeans for taking up wear of the brake pad means interposed between thebrake pad means and the thrust means, said device comprising meansdefining a body combined with the caliper, a system having alongitudinal axis and movable longitudinally relative to the body andcomprising a first element in the form of a screw and a second elementin the form of a nut coaxial with and screwthreadedly engaged with thescrew, one of said elements being rotatable about said axis relative tothe body, means for preventing rotation of the other of said elementsrelative to the body, a ring concentric with the rotatable element,means for keying the ring to the rotatable element so that the ring isslidable relative to the rotatable element along said axis, firstresiliently yieldable means for biasing the ring axially against therotatable element, the rotatable element having an outer peripheralportion having teeth which are parallel to each other and obliquerelative to radial axial planes of the ring, a finger member mounted inthe body for movement radially of the ring and in engaging relation tothe teeth, and second resiliently yieldable means for biasing the fingermember against the teeth.

5. A disc brake as claimed in claim 4, comprising hydraulic means forapplying the brake, the hydraulic means comprising means defining acylinder combined with the caliper, a floating piston engaging therotatable element, and a fluid inlet communicating with the cylinder onthe opposite side of the piston to the rotatable element.

6. A disc brake as claimed in claim 5, further comprising a mechanicalcontrol means combined with the caliper and capable of shifting thefloating piston.

1. A device for taking up wear of brake pad means of a disc brake andadapted to be interposed between the brake pad means and thrust meansfor urging the brake pad means against the disc of the brake, saiddevice comprising means defining a body, a system having a longitudinalaxis and movable longitudinally relative to the body and comprising afirst element in the form of a screw and a second element in the form ofa nut coaxial with and screwthreadedly engaged with the screw, one ofsaid elements being rotatable about said axis relative to the body,means for preventing rotation of the other of said elements relative tothe body, a ring concentric with the rotatable element, means for keyingthe ring to the rotatable element so that the ring is slidable relativeto the rotatable element along said axis, first resiliently yieldablemeans for biasing the ring axially against the rotatable element, therotatable element having an outer peripheral portion having teeth whichare parallel to each other and oblique relative to radial axial planesof the ring, a finger member mounted in the body for movement radiallyof the ring and in engaging relation to the teeth, and secondresiliently yieldable means for biasing the finger member against theteeth.
 2. A device as claimed in claim 1, wherein said means keying thering to the rotatable element comprise axially extending studs integralwith the rotatable element and apertures in the ring into whichapertures the studs extend, the rotatable element having a shoulderagainst which shoulder the ring is biased by the first resientlyyieldable means.
 3. A device as claimed in claim 1, wherein the firstresiliently yieldable means comprise axially extending finger membersand springs biasing the finger members against the ring.
 4. A disc brakecomprising a disc, a caliper, brake pad means, thrust means for urgingthe brake pad means against the disc, and a device means for taking upwear of the brake pad means interposed Between the brake pad means andthe thrust means, said device comprising means defining a body combinedwith the caliper, a system having a longitudinal axis and movablelongitudinally relative to the body and comprising a first element inthe form of a screw and a second element in the form of a nut coaxialwith and screwthreadedly engaged with the screw, one of said elementsbeing rotatable about said axis relative to the body, means forpreventing rotation of the other of said elements relative to the body,a ring concentric with the rotatable element, means for keying the ringto the rotatable element so that the ring is slidable relative to therotatable element along said axis, first resiliently yieldable means forbiasing the ring axially against the rotatable element, the rotatableelement having an outer peripheral portion having teeth which areparallel to each other and oblique relative to radial axial planes ofthe ring, a finger member mounted in the body for movement radially ofthe ring and in engaging relation to the teeth, and second resilientlyyieldable means for biasing the finger member against the teeth.
 5. Adisc brake as claimed in claim 4, comprising hydraulic means forapplying the brake, the hydraulic means comprising means defining acylinder combined with the caliper, a floating piston engaging therotatable element, and a fluid inlet communicating with the cylinder onthe opposite side of the piston to the rotatable element.
 6. A discbrake as claimed in claim 5, further comprising a mechanical controlmeans combined with the caliper and capable of shifting the floatingpiston.